[jira] Commented: (STDCXX-229) better exception error messages

["Martin Sebor (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/STDCXX-229?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12601723#action_12601723 ] 

Martin Sebor commented on STDCXX-229:
-------------------------------------

See [N2629|http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2629.html] for a proposal for an enhancement that would make this possible in front of the committee.

> better exception error messages
> -------------------------------
>
>                 Key: STDCXX-229
>                 URL: https://issues.apache.org/jira/browse/STDCXX-229
>             Project: C++ Standard Library
>          Issue Type: Improvement
>          Components: 18. Language Support, 19. Diagnostics
>    Affects Versions: 4.1.2, 4.1.3, 4.1.4, 4.2.0
>         Environment: all
>            Reporter: Martin Sebor
>             Fix For: 4.3
>
>
> ****Created By: sebor @ Apr 24, 2001 12:11:59 PM****
> Subject: better exception error messages (by using CRTL's strerror()?) (1601)
> Date: Tue, 24 Apr 2001 10:57:13 -0400
> From: cxxrtl@cxxc.zko.dec.com
> To: OEMSUPPORT@roguewave.com
> A customer requested that the what() string for a standard iostream
> error be more descriptive, possibly by using the strerror() or
> perror() function to return the underlying CRTL error string...
> Example:
> #define __USE_STD_IOSTREAM
> #include <fstream>
> #include <string>
> int main() {
>     try {
>         std::ofstream out;
>         out.exceptions(std::ios_base::badbit);
>         out.open("#3.2_BLUE_%.LinkedText");
>         out << "Hello!" << std::endl;
>     }
>     catch (std::exception& e) {
>         perror("The funny looking name that isn't in scope anymore");
>         std::cerr << e.what();
>     }
> }
> ------------------------------- test.cxx -------------------------------
> $ run test
> The funny looking name that isn't in scope anymore: non-translatable vms 
> error code: 0x186D4 %rms-f-syn, file specification syntax error
> iostream object has failbit set
> ****Modified By: sebor @ Sep 29, 2003 11:44:10 AM****
> This would be quite useful but it's non trivial to do in iostreams where exceptions are thrown from stream classes but errors of interest typically occur in stream buffers. Once possibility is to selectively capture and save errno in a thread-safe way (so that it can be later modified w/o affecting the recorded cause of the original error) when it occurs during libc and system calls made from streambuf members and later retrieve it when an exception is about to be thrown from the stream class.

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